The invention relates to a method of controlling a prime mover which includes an internal combustion engine and wherein a setpoint of a torque depends on a variable representing a driver""s wish and operating variables of the internal combustion engine, actuating signals for actuators of the internal combustion engine depend on the setpoint of the torque, and an actuating signal for a motor generator which is arranged on the output shaft of the internal combustion engine depends on the setpoint of the torque. The invention also pertains to a device for controlling a prime mover which includes an internal combustion engine, in which there is provided a device for determining a setpoint of a torque on the basis of a variable representing the driver""s wish and operating variables of the internal combustion engine, a device for generating actuating signals for actuators of the internal combustion engine on the basis of the setpoint of the torque, and a device for generating an actuating signal for a motor generator on the output shaft of the internal combustion engine, specifically on the basis of the setpoint of the torque.
A method of controlling an internal combustion engine is disclosed in the commonly assigned, copending patent application Ser. No. 09/160,878 (published as WO 97/36762 and German DE 196 12 455 A1). A setpoint of a torque is determined on the basis of the position of a gas pedal, the rotational speed and further operational variables such as the air mass flow, the coolant temperature and the oil temperature. Depending on the desired torque, a drive signal for a throttle valve actuator is determined. The torque to be set via the air mass flow is determined by taking into account the desired torque and the derivative-action values of the torque, which are required by functions for controlling the internal combustion engine, such as traction control, engine speed limitation, vehicle speed limitation and a catalytic converter heating function. In addition, a setpoint of the torque, which is to be adjusted rapidly, depends on the desired torque and torque requirements of the further functions for controlling the internal combustion engine. An actuating signal for a spark plug depends on the setpoint of the torque. By changing the ignition angle it is possible for the torque actually produced in one cylinder of the internal combustion engine to be changed within one crank shaft segment. The time period of a crank shaft segment is defined, for example, by the time interval between the ignition cycles of two cylinders which are adjacent in the ignition sequence.
Because of the inertia of the intake tract, the setpoint of the torque to be set via the air mass flow can be set only slowly. If the torque which is actually to be generated by the internal combustion engine has excessively high dynamics, then the derivative-action values must be chosen to be high in order to be able to set the torque with a high quality. However, this results in high exhaust gas emissions from the internal combustion engine and high fuel consumption.
The object of the invention is to provide a device and a method for controlling a prime mover which overcome the above-noted deficiencies and disadvantages of the prior art devices and methods of this kind, and which ensure convenient and simultaneously low-emission operation of the internal combustion engine with a high efficiency of the prime mover.
With the above and other objects in view there is provided, in accordance with the invention, a method of controlling a prime mover having an internal combustion engine, which comprises:
determining a setpoint of a torque in dependence on a variable representing a driver""s wish and operating variables of an internal combustion engine;
defining actuating signals for actuators of the internal combustion engine in dependence on the setpoint of the torque;
determining an estimated value of a maximum or minimum torque that can be set via the actuators of the internal combustion engine within a predefined time period; and
defining an actuating signal for a motor generator connected to an output shaft of the internal combustion engine in dependence on the setpoint of the torque and the estimated value of the maximum or minimum torque.
In accordance with an added feature of the invention, the actuator is a spark plug or an injection valve, and the method further comprises determining an estimated value of the actual motor generator torque, and setting an actuating signal for the actuator in dependence on the setpoint of the torque and the estimated value of the actual motor generator torque.
In accordance with an additional feature of the invention, the actuating signal for the motor generator depends on the difference between the setpoint of the torque and the estimated value of the maximum or minimum torque.
In accordance with another feature of the invention, the motor generator as operated as a motor if the estimated value of the maximum torque is less than the setpoint of the torque. The motor generator is operated as a generator if the estimated value of the minimum torque is greater than the setpoint of the torque. Furthermore, the motor generator is operated as a motor if the difference between the setpoint of the torque and the estimated value of the maximum torque is greater than a predefined threshold value.
In accordance with a concomitant feature of the invention, the predefined time period is defined as the time period of one crank shaft segment.
With the above and other objects in view there is also provided, in accordance with the invention, a device for controlling a prime mover having an internal combustion engine, comprising:
a device for determining a setpoint of a torque in dependence on a variable representing a wish of a driver and operating variables of the internal combustion engine;
a device for generating actuating signals for actuators of the internal combustion engine in dependence on the setpoint of the torque;
a device for determining an estimated value of a maximum or minimum torque that can be set via the actuators of the internal combustion engine within a predefined time period; and
a device for generating an actuating signal for a motor generator, arranged on an output shaft of the internal combustion engine, in dependence on the setpoint of the torque and the estimated value of the maximum or minimum torque.
In summary, the objects of the invention are satisfied with the novel method and device which is distinguished by the fact that an actuating signal for a motor generator which is arranged on the output shaft of the internal combustion engine is determined as a function of the setpoint of the torque. The motor generator has a response time which is considerably lower than the time period until a step in the setpoint of the torque is adjusted via the air mass flow. It is therefore possible for the derivative-action value in the torque to be adjusted via the air mass flow to be chosen to be lower without, in the process, having to accept penalties in terms of convenience.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and device for controlling a prime mover, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.